hadoop relational database

"　　8.getrange key 0 4 #---------------------Gets the value at the specified range position127.0.0.1:6379[2]> set name ' 12345678 ' ok127.0.0.1:6379[2]> getrange name 1 3 "234"　　9.mget key 1 Key 2 .... #---------------------the value of the bulk fetch key127.0.0.1:6379[2]> mget We er rt1) "ew" 2) "ER" 3) "RT"10.INCR Key #---------------------do self-add 1 for the specified key value127.0.0.1:6379[2]> Set ID 12ok127.0.0.1:6379[2]> incr ID (integer) 13127.0.0.1:6379[2]> incr ID (integer) 14127.0.0.

Label:First normal: There are no duplicate columns.Second paradigm: To have a unique identity.The third paradigm: not dependent on non-primary keys.Implemented the third paradigm, which shows that the first and second paradigm have been realized.does not conform to the third paradigm, the database table will have a pruning exception, and generate a large amount of redundant data.For a better understanding of the meaning of the three paradigms, please

Label:Requirements: Export the TBLs table from the hive database to HDFs;$SQOOP 2_home/bin/sqoop. SHSqoop:Theset server--host hadoop000--port 12000--webapp sqoopServer is set SuccessfullyCreate connection:Sqoop the>Create connection--cid 1Creating Connection forConnector withID 1Please fill following values to create new connectionObjectName: tbls_import_demoConnection configurationjdbc Driver Class: com.mysql.jdbc.DriverJDBC Connection String: jdbc:m

Tags: des blog http using strong dataI believe that the development experience of friends have encountered such a demand. Suppose you are developing a comment function for a news site, and readers can comment on the original text or even reply to each other.This need is not simple, mutual reply will lead to an infinite number of branches, an infinite number of ancestor-descendant relationships. This is a typical recursive relational data.For this prob

Relational database,1. Create a table 1 create table student (2 sno char (8), 3 sname char (8), 4 sbirth date, 5 ssex char (2), 6 sdept char (30) 7 ); 2. delete a table 1 drop table student1; 3. Common Data Types 4. Declare the primary code 1 create table student (2 sno char (8) primary key, 3 sname char (8), 4 sbirth date, 5 ssex char (2), 6 sdept char (30) 7 ); 5. Declare external code 1 cre

(Original) based on the tree structure data stored in the chain of the relational database system, calculate the algorithm of all the nodes of the subtree under a node (t-SQL language implementation) Create Function f_subtree (@ dpcode varchar (9)/* tree structure data, which is used to find the User-Defined Function of all the nodes of the subtree under a node */Returns @ new table ([dpcode] [varchar] (9),

This week is reviewing the "Introduction to Database System" This course, see this section of relational operations, for the addition of operations is not very understanding. Through Baidu, I do not feel that it is easier to understand the explanation. Here, I would like to share my understanding, if there is a mistake in the place, but also want to see this blog to give you guidance. First of all, I h

number, manufacturer's name, component number, and manufacturer's address, but also manufacturer's name, the manufacturer's address, so there is a non-primary attribute transfer dependency on the main attribute, which does not conform to the third normal form requirementAfter modification:BC Paradigm: Based on the first paradigm, each non-trivial dependency must have a key code on the left side, and each determinant must contain a key code. Wikis: Any property, including non-primary and primary

Tags: type brackets unique order Chinese word breaker query files multiple columnsImprove query speed, facilitate sorting and grouping. (The process of sorting and grouping, if not indexed, results in temporary tables and filesort)Based on business logic, analyze the frequency and order of column queries, and build indexes and composite indexes.Primary key index (primary key),----> No index name is required because there is only one primary key indexUnique index (single key)---->unique Key Email

Label:Count: Count rows Select COUNT (*) from student Select count (age) from student/* will not count null values */ Sum: Returns the sum of the values in the column and automatically skips the null value (numeric +null=null) Select SUM (age) from student Avg: Returns the average of all values in the result set Select AVG (age) from student Max/min: Returns the maximum/small value in all values Select Max (age) from student GROUP BY: Data Group query Select Age,name,count (*) from the student

 1. Master-slave replication is MongoDB The most commonly used replication method, which is very flexible and can be used for backup, failure recovery, read extension, etc.2 The most basic way to set up is to establish a master node and one or more slave nodes, each from the node to know the address of the master node. The primary server is started by running Mongod–master. Running mongod–slave–source master_address initiates the slave server, where master_address is the address of the prima